Pet door



FIG. 1 is a front perspective view of a pet door showing the new design;

FIG. 2 is a top perspective view thereof;

FIG. 3 is a bottom perspective view thereof;

FIG. 4 is a left side perspective view thereof;

FIG. 5 is a right side perspective view thereof; and,

FIG. 6 is a top, left, perspective view thereof.

The broken lines shown the drawings depict portions of the pet door that form no part of the claimed design. 

CLAIM The ornamental design for a pet door, as shown and described. 